Wavelength-Sensitive Photocatalytic Degradation of Methyl Orange in Aqueous Suspension over Iron(III)-doped TiO₂ Nanopowders under UV and Visible Light Irradiation

Abstract

Well-crystallized iron(III)-doped TiO2 nanopowders with controlled Fe3+ doping concentration and uniform dopant distribution, have been synthesized with plasma oxidative pyrolysis. The photocatalytic reactivity of the synthesized TiO2 nanopowders with a mean particle size of 50-70 nm was quantified in terms of the degradation rates of methyl orange (MO) in aqueous TiO2 suspension under UV (mainly 365 and 316 nm) and visible light irradiation (mainly 405 and 436 nm). The photodecomposition of MO over TiO2 nanopowders followed a distinct two-stage pseudo first order kinetics. Interestingly, the photocatalytic reactivity depends not only on the iron doping concentration but also on the wavelength of the irradiating light. Under UV irradiation, nominally undoped TiO2 had much higher reactivity than Fe3+ -doped TiO2, suggesting that Fe3+ doping (> 0.05 at. %) in TiO2 with a mean particle size of approximately 60 nm was detrimental to the photocatalytic decomposition of methyl orange. Whereas, under visible light irradiation, the Fe3+ -doped TiO2 with an intermediate iron doping concentration of approximately 1 at. % had the highest photocatalytic reactivity due to the narrowing of band gap so that it could effectively absorb the light with longer wavelength. A strategy for improving the photocatalytic reactivity of Fe3+ -doped TiO2 used in the visible light region is also proposed.

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Photocatalytic activity of V5+, Mo6+ and Th4+ doped polycrystalline TiO2 for the degradation of chlorpyrifos under UV/solar light

“…4 and 5). The curves show two different linear stages which indicate that the photocatalytic degradation follows first-order kinetics in two stages [32,33]. The rate constant for the second stage is twice than that of first stage for TiO 2 as shown in Table 4.…”

Investigating the Water Sealing Capability of Polymer Concrete

“…The high efficiency of the FeCl 2 as catalyst could be due to the high solubility of this catalyst with respect to Fe 2 O 3 NWs. The photocatalytic activity was quantitatively evaluated by calculating the pseudo first-order rate constants (k) according to the following equation (Wang et al, 2006;Asiri et al, 2011;Salehi et al, 2012):…”